Yes, you can buy any firearm you want from an out-of-state FFL. The issues are, if you are not a resident of that state, you can only purchase and take with you rifles and shotguns. If your state of residence has restrictions on what firearms you are “allowed” to possess, then you cannot legally purchase it. If you buy a handgun, it must be shipped to an FFL in your state of residence, where a background check will be done, and then you can have it transferred to you. If you have a home in the other state, and documentation of a physical address in the other state, you can buy whatever you want.
This topic was covered in another thread.